Anti-oxidants versus Pro-Oxidants
ByA reader asked an interesting question recently that I thought would make a good post. The question involved the use of antioxidants, either for dogs with cancer or to help prevent cancer.
Lets get an overview to clarify this frequently-muddied picture.
A free radical is a reactive molecule that tends to damage cell parts. When DNA is damaged, this can mean damaged genes. If the genes controlling cell multiplication are harmed, cell growth can get stuck in the “on” position.
When cell growth is stuck “on”, this spells cancer.
Cancer cells are very active doing all this growing. One of the by-products of all this activity in an increased load of free radicals within the cancer cell.
Cancer cells are not good at handling much more free radicals, since they already have more in them than normal cells.
The body is able to quench free radicals with substances called antioxidants. Antioxidants lessen the amount of free radical-induced injury.
A pro-oxidant has the opposite effect. It tends to increase the amount of free radicals.
Since pro-oxidant strategies increase free radicals, it would seem that the way to kill cancer cells is by bombarding them with pro-oxidants. This would lead to more free radicals within cancer cells, and injury to the cancer cells.
The mechanism of many chemotherapy drugs, as well as radiation, in destroying cancer cells is by causing free radical increase within cancer cells. This is the same mechanism in many of the apoptogens discussed in The Dog Cancer Survival Guide.
Now, healthy cells also suffer when there is free radical excess. It is just they have more of a natural buffer within them than the free-radical filled, madly proliferating cancer cells do.
If the natural body buffers are depleted, this can lead to lack of overall body health in the fight against cancer. That is why maintenance levels of certain antioxidants actually help during the fight against cancer.
We want to preserve overall body health, and minimize side effects of chemo and radiation toxicity. Many chemo and radiation side effects are due to injury of normal body cells by the free radicals caused by these treatments. Here is a good read on the topic.
Maintenance antioxidants help, and this has been evaluated and shown to be accurate, even when these antioxidants were used along with chemotherapy.
However, only some so-called antioxidants should be used in high levels (way above maintenance levels) during cancer treatment with chemotherapy or radiation. At high levels, these substances no longer have antioxidant effects.
Rather, they typically have pro-oxidant effects. Selenium, EGCG, IV vitamin C and others are like this. Some so-called antioxidants at high levels have other ways of killing cancer cells, like inhibiting certain enzymes (curcumin inhibits topoisomerase II).
If we are relying on conventional care, we don’t want to create abnormally high antioxidant effects in the body, as there could be interference with radiation and chemotherapy. Since these tools work by increasing free radicals, excessive antioxidants may decrease efficacy. Read more here.
It becomes clear that dosages are a central issue with antioxidants. Maintenance levels and high levels do different things.
What about cancer prevention and longevity?
When a dog gets cancer, it is the end result of many damaging events. It likely takes a lifetime of steps, which is why cancer is more typical in older dogs.
It has been said that there are many cancer cells developing in the body daily. True. Developing, but not yet developed. That means they are not actual cancers yet. They are cells on their way to becoming cancer cells.
In the path to true, clinical cancer (the end stage), damaging steps are free radical injury to genes controlling cell growth. There needs to be multiple hits over time in certain locations on the DNA for the damage to finally create a cell growth signal stuck on “on”.
Thus, before true, clinical cancer actually develops, you want antioxidant effects, not pro-oxidant ones, in general.
In contrast, after cancer clinically develops, one could choose pro-oxidants as the anti-cancer weapon.
I hope this helps everyone wondering about vitamins, antixodants, and cancer.
Best,
Dr D
About the Author
Dr. Demian Dressler, DVM is known as the "dog cancer vet" and is author of Dog Cancer Survival Guide: Beyond Surgery, Chemotherapy & Radiation. Visit his blog and sign up free to get the latest information about canine cancer. Go to http://DogCancerBlog.com.
6 Comments
June 29th, 2009 at 6:57 pm
I recently lost a dog to mailgnant histiocytosis and I have her half sister. I really want to help her not get cancer & wonder what food or suppliment you would suggest as a preventative.Thank you for any suggestions…Sincerely, Chris Ambrose
June 30th, 2009 at 1:58 pm
My dog recently had a pheriphial tumor on his leg removed.
No rad. or chemo… now what for his diet.. I took all grains
away. Do you know of transfer factors?
July 3rd, 2009 at 2:25 pm
Does anyone know about K-9, transfer factors for treatment
toward getting a dog’s immune system in better shape to fight
cancer? The surgeon for my dog was not very impressed with
this information…n
December 6th, 2009 at 2:38 pm
[...] Vitamin C is known as an anti-oxidant. While it is at lower doses, the anti-cancer effects at the needed super-doses are actually pro-oxidant. (For more on these concepts, click here) [...]
January 21st, 2010 at 8:07 am
Wow. My greyhound, Silver, had a mast cell tumor removed from his rear right leg last April ~ 10 months ago. I’ve cut way back on his carbs, but because he has “slightly challenged” kidney function (he was losing too much protein in his urine) I am also supposed to keep his protein down as low as possible. That in itself is a juggling act.
I give him 2 Co-Q10+ capsules a day (Fish oil, CoQ10 and vit. E) and a Marin tablet, plus he is using the Chinese Herbals Power Mushrooms and Blood Palace for follow up in lieu of any Chemo. So far, so good. I’m currently using Dr. Harvey’s complete Veg-to-Bowl dehydrated fresh dog food with a very small amount of good quality kibble, grass fed beef from a local farm and occasionally Eagle Brand canned (now Holistic Select). It does get confusing, and sometimes expensive (I have 4 sighthounds and am on fixed income) — finding the right balance between low carb and low protein and now questioning his supplements is — well, distressing. Love to hear a response on this.
January 22nd, 2010 at 9:44 pm
Dear Carla,
You are in the land of medicine: the gray zone. More data needs to be considered. First, if your dog has a Hard to Cure Cancer, you may want to consider a more Full Spectrum approach than a replacing approach (supplements instead of chemo). I am wondering about the logic in the CoQ10 selection and in some of the other choices. Why not pick some supplements that have some more direct evidence against cancer cells? Similarly, why not some support to stabilize mast cells so they don’t secrete as much histamine? Although I do not have a cure for systemic cancers, it may be worthwhile to consider some of these questions. Luteolin, EGCG, artemisinin, cimetidine, ginger, slippery elm…just to name a few that pop into mind for dogs with mast cell tumors. I blogged on these so you can search for them and wrote about them in my e-book.
Anyway, to answer your question directly, you may want to find out whether the urine protein was tested using a urine protein/creatinine ratio test. Urine protein readings in a normal urinalysis have lots of positive protein readings that will have nothing to do with kidney function. Perhaps there is more evidence for kidney disease in your dog that I don’t know about?
Bottom line, try to get an idea of the objective severity of the two conditions from your vet, which I cannot do. Which is worse? Then, go with that.
Hope this helps,
Best,
Dr D